The before mentioned coolable wall elements are well known as ring segments in the prior art. These ring segments, also known as blade outer air seals, are usually arranged within the gas turbine for bordering the hot gas path of a turbine section. These ring segments are arranged along the circumferential direction whereby all segments of a circumference create a ring. Inside of said ring, turbine blades mounted on the rotor of the turbine moves along their hot gas path surface when said turbine rotor is rotating during operation.
Usually said ring segments are carried by a turbine vane carrier. Usual turbine vane carriers are in cross section perpendicular to the machine axis in annular shape and for stationary gas turbines split into a lower half and an upper half. The turbine vane carrier has grooves extending in the circumferential direction in which the ring segments could be slid to their dedicated position one by one to form outer border of the hot gas path.
Due to the hot gas flowing along the ring segments, said ring segments have to be cooled to reach their predetermined life time. For cooling purposes it is known to attach an impingement plate on the outer side of the ring segments in such a way, that the ring segment could be cooled by air impinging on the cold side of the ring segment thereby carrying away the thermal energy of the wall of the ring segment.
To provide a reliable ring segment the impingement plate must be held in the fixed position without significant motion. For this, in the past impingement plates were welded or brazed directly to the main body of the ring segment.
Further, WO 2014/186166 A1 discloses a cooling arrangement having a snap-in impingement plate. In detail each of the four edges of the impingement plate sits in a corresponding groove without being welded or brazed. However, the impingement plate needs folded edges to clamp the respective edges into corresponding grooves. The provision of these folded edges seems expensive.
Besides this, EP 2 789 803 A1 discloses a u-shaped impingement ring element, which is assembled into a circumferential groove of a ring shaped carrier through which cooling air is guided to the impingement ring element. The ring element comprises a retainer tab as a stopping element prohibiting a radial movement between the impingement ring element and its groove, the groove being opened in radial direction.